Plasticised cable

Figure 5.5 Dependence of coefficient of swelling on stress for plasticised cable. Section...

Figure 5.6 Dependence of explosive effort of extrudate from pressure for plasticised cable. Section of an item - 5588585. S, = 70 mm...

Successful combination of a chromatographic procedure for separating and isolating additive components with an on-line method for obtaining the IR spectrum enables detailed compositional and structural information to be obtained in a relatively short time frame, as shown in the case of additives in PP [501], and of a plasticiser (DEHP) and an aromatic phenyl phosphate flame retardant in a PVC fabric [502], RPLC-TSP-FTIR with diffuse reflectance detection has been used for dye analysis [512], The HPLC-separated components were deposited as a series of concentrated spots on a moving tape. HPLC-TSP-FTIR has analysed polystyrene samples [513,514], The LC Transform has also been employed for the identification of a stain in carpet yarn [515] and a contaminant in a multiwire cable [516], HPLC-FTIR can be used to maintain consistency of raw materials or to characterise a performance difference. 

Most trading polymers contain a variety of additives, e.g., plasticisers, lubricants, stabilisers, etc., and it is these additives that promote bacterial attack on the polymer. At the same time, degradation by other routes provides pathways for bacterial attack by creating hydrophilic surfaces. Because many industrial and domestic services are supplied by underground plastic pipes and cables, care must be taken when choosing additives to make sure that the polymer is not vulnerable to attack. 

The first is metakaolin. This is a partially calcined product that forms above about 500 °C. Only about 10% of the original hydroxyl groups of the kaohnite are retained and much of the crystalline nature of the structure is destroyed. Metakaolin is considerably more reactive than the original kaolin and appears to have an especially reactive surface. It is generally used uncoated and finds most use in plasticised PVC cable insulation, where it is reported as giving uniquely useful electrical properties [86]. 

PVC-U formulations have low flammability due to the chlorine content. The addition of plasticiser in PVC-P formulations necessitates the use of flame retardant and smoke suppressant additives. These additives are known as functional fillers and a correct balance is necessary to achieve all the end-use specification requirements. They are predominately used in cable, conveyer belting and roofing membrane formulations to give resistance to fire initiation and propagation. It is also important to reduce dripping in a fire situation and that as little smoke as possible is generated. Antimony trioxide has been used extensively, usually in combination with phosphate ester plasticisers, giving excellent fire performance and mechanical properties. 

Ethylene copolymers (high molecular weight flexibilisers) have been proposed to replace liquid plasticiser for low smoke FR PVC cable formulations (238). 

Ethylene copolymers were compared with liquid plasticisers for use as additives to improve the flexibility of poly(vinyl chloride) (PVC) for electrical cable insulation applications. The PVCs were assessed by determining smoke generation, flammability, tensile properties and the low temperature brittle point. The ethylene copolymers gave similar peak heat release rates, but the peak smoke and the total smoke generation were lower. They also gave similar or increased strength, similar elongation and flexural modulus, and lower brittle point temperatures. 4 refs. 

Oparex 15 calcined calcium sulphate (Yesos Ibericos) was evaluated as a filler in plasticised PVC cable insulation compounds in comparison with two grades of calcium carbonate. Improvements were observed in tensile, electrical and low temperature properties, flammability and heat ageing characteristics and chemical resistance for calcium sulphate filled compounds, while no significant differences in water absorption and hydrolysis were noted. Studies of rheological properties showed improved processability in mixing and extrusion trials. URALITA... 

The primary particle size of Winnofil stearate coated precipitated calcium carbonate from Zeneca Resins is in the region of 0.075 micron. When compounded into natural and synthetic elastomers, the hydrophobic surface coating assists wetting and aids dispersion. When compounded into plasticised PVC for cable sheathing, the PCC allows for formulations with minimal potential for acid gas release in combustion conditions. In rigid PVC, stearate coated PCC has been used in compounding as an alternative to conventional acrylic processing aids and as a means to reduce impact modifier levels. 

The influence of moisture on the dielectric properties of three experimental resin casting systems and an epoxy based laminate is investigated in this chapter to see if the mechanisms described above, can be recognised. Besides, the resistivity of an epoxy based tank coating and that of plasticised PVC cable insulation material in contact with water is described. 

The Ki-value determination of PVC cable compounds The specific volume resistivity is the most important electrical property of an electrical grade PVC. It is measured on a heavily plasticised product, the cable compound, pressed to a 2 mm. thick sample sheet. Cable manufactures usually test the resistivity of these compounds on cable samples and express the results in a so-called Ki-value. The Ki-value is in fact a volume resistivity value (see below) but measured on a cable sample with tapwater as low potential measuring electrode. A series of Ki-value determinations was performed to investigate the different parameters influencing this quantity. 

The copper conductor in electric cable initially acts as a heat sink in a fire. Later on, it transfers heat to other parts of the insulation. Plasticisers, in flexible PVC electrical insulation, do not contain chlorine, so reduce the... 

Why is plasticised PVC suitable for insulating domestic mains cable, but not as a dielectric in a TV aerial ... 

Chlorinated paraffins (mainly CPVC) are widely used in PVC to give greater resistance to ignition and combustion than general-purpose plasticisers. However, the effects of chloroparaffins on health are still a controversial issue and their use as flame-retardants in PVC applications for cables, wall coverings and flooring is declining. 

Citrates are considered low-hazard plasticisers. Acetyl tributyl citrate has been used in food packaging film while butyryl tri-n-hexyl citrate has been evaluated for medical devices. Phosphates (tricresyl or triphenyl) are favoured where flame retardancy is at a premium, notably cable insulation. 

Phenolic antioxidants such as bisphenol A and BHT have traditionally been used to protect plasticisers against thermal decomposition in high temperature PVC applications like wire and cable insulation and vehicle parts. This is because branched plasticisers imdergo autoxidation and eventually form acids. BHT (butylated hydroxy toluene) is now being replaced in this role by high molecular weight phenols with greater permanence. 

Plasticiser end-use markets include wire and cable, floor and wallcoverings, construction products such as roofing membranes, automotive parts, packaging, medical appliances, gloves, pond liners, sports goods and footwear. Table 5.2 indicates some of the applications of a variety of plasticisers. 

The most prominent application end-uses for PVC blends require permanent plasticisation. Butadiene/acrylonitrile copolymers have been compounded as permanent plasticisers for PVC wire and cable insulation, applications requiring food contact, and in pond liners used for oil containment [21]. Compounding with nitrile rubbers in plasticised PVC provides improved ozone, thermal ageing and chemical resistance for applications such as fuel hose covers, gaskets,... 

It is estimated that about 5%t of the total value of a real estate belongs to electrical cables and wiring. Within the polymers used for electrical cables and wiring, PVC electrical products are the most durable that provide electrical and fire safety at low cost and contribute to the life safety in building design. PVC-U is inherently flame retardant, but PVC-P looses this property somewhat (because of the plasticisers used) and are used... 

PVC-P, on average, contains 55 phr (parts per weight per hundred of PVC) plasticiser. PVC has the ability to accept high levels of plasticiser (100 phr and even above). The most common plasticisers that are used today in PVC are DOP (nsed in the mannfacture of flooring and carpet tiles), DEHP (used mainly for any flexible PVC applications), di-isodecyl phthalate (DIDP), used mainly in wire and cable production, carpet backing and pool liners, di-isononyl phthalate (DINP), and butyl benzyl phthalate (used mainly in vinyl tile production), and di-n-hexyl phthalate (used in flooring applications). There are also several plasticisers that are specific for almost no toxicity, such as tri-(2-ethylhexyl) trimellitate (TEHTM), a polymeric adipate, and acetyl triburyl citrate (ATBC), which are economically unfeasible for their industrial applications, i.e., TEHTM is some three times as expensive as DEHP, and polymeric adipate four times as expensive. Analytical techniques are available to detect traces of plasticisers at the parts per billion level [43]. 

There is some overlap in the performance of metakaolinite and calcined clay in certain polymers and hence some contiguous applications such as low-voltage rubber cable insulation, but there are significant differences, which leads to separate use patterns. Thus, metakaolinite is mainly used in PVC cable insulation because it improves (uniquely) the electrical resistivity of plasticised PVC, while calcined clay is used in polyethylene (PE) film, rubber cables, rubber pharmaceutical applications and rubber extrusions for a variety of reasons linked to its shape, size and chemical inertness. The refractory product finds limited use in epoxy and unsaturated polyester mouldings, which have to resist abrasion and chemical attack. 

IR spectroscopy may be used for detection of plasticisers in soft PVC cables [75], but does not distinguish clearly between the many possible di-alkylphthalates. With the advent of difference spectroscopy, identification of a plasticiser in a polymer no longer requires isolation of the additive. Identification can readily be made without separation if the polymer is known and a plasticiser-free spectrum is available. This was illustrated for di-2-ethylhexylsebacate in an acrylonitrile-butadiene copolymer [76]. IR can sometimes quantify plasticisers in solid plastic compositions without the need for extraction or dissolution steps. FTIR difference spectroscopy has also been used for quantitative analysis. Another example of difference spectroscopy is the case of two plastic films which differed in printability [77]. Difference mid-IR spectra of the surfaces of the two films in the 1600-1300 cm region revealed a stearate (and eventually a free acid, at 1720 cm ). Surface properties of... 

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